KR100346098B1 - Information recording disk injection molding method - Google Patents

Abstract

The present invention supplies a resin material such as polycarbonate to an injection device in which a vent port is formed in a state where pre-drying is omitted, and melts and kneas the resin material by the injection device, and at the same time, moisture in the resin vaporized by heating. Discharging the volatile component from the vent port to the outside of the cylinder, weighing the molten resin, and injection-filling the inside of the mold into which the molding cavity of the information recording disk is formed. An injection molding method of an information recording disk to be manufactured is provided. It is an object of the present invention to provide a novel injection molding method which enables the production of high quality information recording discs by reducing the number of times of heating and melting of resins, minimizing the thermal history or reducing the degradation of physical properties due to the thermal history. . In addition, the injection molding method uses a screw pre-plasticization injection molding apparatus such as the injection molding apparatus to perform plasticization and injection filling of a resin material in a separate cylinder, so that even in the case of disk molding having a small amount of resin, a long time is required. Stable molding can be performed.

Description

Information recording disk injection molding method

[Technical Field to which the Invention belongs and Conventional Technology in the Field]

The present invention relates to a method for injection molding an information recording disk by omitting preliminary drying of the resin material, and to ejecting a thin information recording disk by separating plasticization of the resin material and injection filling into a mold. It relates to a method of molding.

Conventionally, injection molding of information recording disks, such as optical disks, magnetic disks, magneto-optical disks, etc., is performed in-line in which injection screws are freely rotated or moved back and forth in a heating cylinder having a nozzle and a supply port formed at a rear end thereof. ) A screw injection device was used.

[Purpose of invention]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to reduce the number of times of heat melting of a resin to minimize thermal history or to deteriorate physical properties, thereby producing a high quality information recording disc. It is to provide an injection molding method of.

Another object of the present invention is to provide a novel injection molding method capable of performing stable molding for a long time even when the amount of resin is small by plasticizing and injection filling of the resin material in a separate cylinder.

Detailed description of the invention

According to a first embodiment of the present invention, a resin material such as polycarbonate is supplied to an injection apparatus in which a vent port is formed without preliminary drying, thereby melting and kneading the resin material by the injection apparatus and simultaneously heating the resin material. The volatile components such as water contained in the vaporized resin were discharged to the outside of the cylinder through the vent port, the molten resin was weighed, and then injected and filled into a mold having a molding cavity formed therein. A thin information recording disc is produced.

In the second embodiment according to the present invention, the injection apparatus is a screw preliminary plasticization injection apparatus, which produces a thin information recording disc. In this case, the resin material is melted and kneaded by the plasticizing screw in the plasticizing cylinder in which the vent hole is formed, and at the same time, the volatile component in the resin material is discharged from the vent port to the outside of the cylinder, and the molten resin Is injected into the front of the injection cylinder with a built-in plunger to perform the metering, and to manufacture the thin information recording disk by injection filling the metered resin into the mold having the cavity formed therein using the plunger.

According to a third embodiment of the present invention, an inert gas atmosphere is created inside the cylinder between the resin material supply port and the vent port of the injection apparatus. The inert gas prevents the resin material from oxidizing during melting and kneading. According to still another embodiment of the present invention, a plurality of information recording discs can be produced simultaneously by a mold having a plurality of cavities therein.

In the injection molding method according to the present invention, since preliminary drying by heating before molding is omitted, the thermal history of the resin is minimized, and deterioration of the resin due to heating, in particular, decrease in strength is prevented. In addition, it suppresses the mixing of foreign matters and prevents the occurrence of carbonized sunspots caused by the mixing of foreign matters, which is a conventional problem.

In addition, molding defects due to hydrolysis are also solved, and a high quality information recording disc can be obtained. In addition, since the volatilization and discharge of the residual monomers are carried out at the same time, the amount of molding deposit adhering to the stamper disposed in the cavity of the mold is reduced, and the period of work to be repaired becomes long. In addition, when the resin material is plasticized in an inert gas atmosphere, yellowing due to oxidation is prevented, thermal hysteresis is also reduced, and light transmittance through the disk is improved. Can be obtained.

According to the injection molding method of the present invention, when using such a preliminary plasticizing injection apparatus in which a preliminary plasticizing injection apparatus equipped with a vent port is realized, the resin material is melted and kneaded. In other words, the resin material is plasticized by a plasticizing cylinder which is provided separately from the injection cylinder and which the resin rotates at a substantially fixed position and is formed with a vent port. For this reason, in the case of the resin temperature reaching the front end of the plasticizing cylinder, no deviation by the resin temperature plasticized in the injection cylinder occurs. Therefore, the temperature of the resin metered at the front of the injection cylinder is always uniform via the resin passage equipped with heating means at the periphery, so that even if the thickness of the injection molded disc (0.6 mm) is very thin, no stress remains. Therefore, birefringence is improved and transfer of the pit is performed uniformly.

In addition, since metering is performed by moving the plunger backward by the pressure of the resin pushed from the plasticizing cylinder, variation in weighing is eliminated, and accidental unfilling or overcharging caused by unstable weighing is prevented. As a result, the disc weight variation is improved from ± 0.1 g to ± 0.02 g, and the transferability is also improved, thereby enabling stable molding over a long period of time.

Since the resin used in the injection molding is composed of small particles, granulated sugar type, and unreacted monomer, there is a difficulty in molding the resin. pellets) and then used as a resin material. Since the resin adjusted to pellets is hygroscopic, it is dehumidified by preliminary drying to remove moisture before being used for molding. However, the moisture remaining in the resin material may cause silver streaking or yellowing during molding, which may cause molding failure, and also cause hydrolysis of the resin during plasticization, thereby causing a decrease in strength of the molding disc. do. In addition, when the drying apparatus is poorly managed, fine foreign matter in the air adheres and carbonizes, resulting in black spots on the molded product, causing the molded product to be defective. In particular, when the molded article is an information recording disk such as an optical disk, a magnetic disk, a magneto-optical disk, or the like, even a fine black spot causes a read failure.

For this reason, the resin material must be heated at least three times, including at the time of injection molding, so that its physical properties deteriorate, and thus, particularly, the strength decreases easily, thereby causing problems in transparency.

Moreover, when using a conventional in-line injection device, the resin material fed into the cylinder is melted and kneaded through a supply port disposed at the rear of the cylinder. That is, it is plasticized by the rotation of the injection screw, and the injection screw is moved backward by the resin pressure. For this reason, the resin is metered inside the front side of the cylinder, and the metered material is injection-filled by the screw forward into the cavity of the mold adjacent to the nozzle tip to produce the necessary information recording disc. . Several compression molding operations are performed to compress the resin injected into the mold in order to improve the transfer degree and the birefringence of the thin disk of approximately 1.2 mm thickness.

However, in the molding in which plasticization of the resin and injection charging of the resin are performed by the same screw, however, the injection screw is retracted by the pressure of the plasticized resin to measure the resin, so that injection of a disc or the like with a small amount of resin is performed. In the case of molding, even in a small injection apparatus, deviations occur easily during weighing, and the injection charge amount into the cavity becomes unstable, causing sudden unfilling or overcharging, and it is difficult to perform stable molding for a long time.

In addition, non-uniformity also occurs in the plasticized resin temperature, and the retraction of the injection screw causes the L / D ratio (length / diameter ratio) to change, which tends to lower the temperature at the completion of weighing than at the start of weighing the resin. Will be. As a solution of this problem, although a screw having a mixing means or a spiral barrier type screw or the like is employed, the effect is still insufficient and improvement is desired.

Fig. 1 is a longitudinal sectional view of the main part of an injection molding machine in which a vented screw is used, which is used in the execution of the information recording disk injection molding method according to the present invention.

Fig. 2 is a longitudinal sectional view of a preliminary plastic injection molding apparatus used in the practice of the injection molding method of the information recording disk according to the present invention.

3 is a partial longitudinal cross-sectional view showing the relationship between the preliminary plasticizing injection molding apparatus and the mold of the present invention.

〈Description of the symbols for the main parts of the drawings〉

1: heating cylinder 2: injection screw

3: support cylinder 4: supply port

4a: inert gas feeding unit 5: vent port

5a: decompression suction unit 6: hopper

7: nozzle 8: mold

9: cavity 11: injection device

12: plasticizer 13: resin passage

14: fixed plate 15: nozzle touch cylinder

16: base block 17: expectation

22: injection cylinder 22a: rim

23: piston 25: inlet

26: resin extraction hole 27: band heater

30 screw 31 outlet

31a: flow gap 32: plasticizing cylinder

33: support cylinder 33a: rotation axis

33b: member 33c: stopper

34: hydraulic cylinder 34a: piston

35: rotary drive unit 35a: drive shaft

36: band heater 37: supply port

38: check valve 39: ring valve seat

40: capillary tube 40a, 40b: joint

41 band heater 42 mixing member

50: vent port 50a: decompression suction unit

51: disc mold 52: cavity

53: hot runner

Figure 1 shows a vent type injection molding apparatus capable of implementing the injection molding method of the present invention. Reference numeral 1 is a heating cylinder, and a plurality of band heaters (not shown) are mounted around the outer surface. The heating cylinder (1) has a built-in injection screw (2) capable of rotating and moving back and forth. The rear end of the cylinder is engaged with the support cylinder 3, and the supply end 4 of the material is opened upwardly at the rear end thereof.

A vent port 5 is formed in the upper portion of the cylinder in front of the supply port 4. The vent port 5 and the supply port 4 are connected to the pressure reduction suction unit 5a and the inert gas pressure feeding unit 4a, respectively.

In such a vent type injection apparatus, the injection screw 2 is rotated in the same manner as in the prior art and an inert gas such as nitrogen gas is pumped from the supply port 4 into the cylinder. In the vent port 5, the pressure reduction in the cylinder is performed. That is, the cylinder inside is brought to a vacuum state.

In this way, an undried resin material, for example, a polycarbonate which has been previously fed into the hopper 6, is fed into the cylinder through the feed port 4. Subsequently, the resin material pelletized by the rotation of the injection screw 2 is fed forward into the cylinder and compressed.

In the process leading to this compression, the resin material is kneaded and melted simultaneously by the heat transmitted from the heating cylinder 1 and the heat generated by the rotation of the screw. This melting and kneading is performed in an inert gas atmosphere supplied in the cylinder between the supply port 4 and the vent port 5, so that oxidation by heating is prevented. In addition, volatile components such as moisture vaporized by heating and compression are released into the cylinder.

These gases are sucked together with the inert gas through the vent port 5 which is constantly pressurized and discharged to the outside of the cylinder so that they do not remain in the plasticized resin in front of the vent port 5. As a result, even the resin containing water does not cause yellowing due to oxidation or weakening due to hydrolysis in the resin metered in the front of the cylinder by the screw 2 moved backward due to the resin pressure.

The improved resin is filled into the cavity 9 in the mold 8 via the hot runner 10 from the nozzle 7 provided at the tip of the cylinder by the forward movement of the injection screw 2. The cavity 9 is for a thin information recording disk, and since one side of the cavity is provided with a stamper in a taut state, the disk formed in the mold is transferred to one side of the pits formed on the stamper, and is made of polycarbonate. And an information recording disk of approximately thin thickness (approximately 0.6 to 1.2 mm).

As described above, even if the resin used for injection molding is undried, there is no problem in performing injection molding. Such a resin itself is also preferable in terms of physical properties because it has a smaller thermal history than when pre-dried. Since the transparency of polycarbonate is not impaired, injection molding of a high quality optical disk, a magneto-optical disk, etc. with improved birefringence can be achieved. In addition, since the preliminary drying is omitted, the molding cost is also reduced.

Next, a preliminary plasticizing injection apparatus possible in another embodiment of the present invention will be described with reference to FIG. Reference numeral 11 denotes an injection device, in which a plasticizer is disposed in parallel. The injection apparatus and the plasticizer are communicated with each other by the resin passage 13 provided over the tip portion thereof.

The injection device 11 includes an injection cylinder 22 having a plunger 20 for injection and moving in a forward and backward direction and having a nozzle at a tip end thereof, and a plunger 20 at a rear end of the injection cylinder 22. It consists of the injection hydraulic cylinder provided with the piston 23 connected.

The injection cylinder 22 is formed with an inlet 25 of the resin passage 13 located above the tip corresponding to the forward movement limit of the plunger. The inlet 25 is formed to be inclined toward the inner circumferential edge of the rims 22a and rim of the injection cylinder 22 so that plasticized resin fed through the resin passage 13 flows along the inner circumferential surface of the resin passage. have.

A resin extraction hole 26 is formed above and below the plunger stroke of the injection cylinder 22, and a plurality of band heaters 27 are provided around the cylinder to the rear of the resin extraction hole 26. To provide longer heating range.

The plasticizing device 12 includes a plasticizing cylinder 32 including a freely rotating plasticizing screw 33 and a discharge port 31 formed at a tip thereof, and a rear end portion of the plasticizing cylinder 32 to support the plasticizing cylinder 32. A support cylinder (33) installed in the cylinder, a hydraulic cylinder (34) connected to the rear end of the support cylinder (33) to move the screw forward and backward, and a screw (30) attached to the rear end of the hydraulic cylinder (34). It consists of a rotary drive unit 35.

The drive shaft 35a of the rotary drive unit 35 has a rear end penetrated into the piston 34a of the hydraulic cylinder 34 and connected to the rotary shaft 33a accommodated in the support cylinder 33 freely in the axial direction. It is. The front end of the rotating shaft 33a is connected to the rear end of the screw 30. The rotating shaft 33a is connected to the piston 34a only in the axial direction through the member 33b, and is moved back and forth together with the piston 34a to move the screw 30 forward and backward. The member 33b is provided with a stopper 33c for limiting the forward movement of the screw 30 to a predetermined range.

A plurality of band heaters 36 are attached to the outer circumference of the plasticizing cylinder 32, and a supply port 37 is upwardly disposed at a rear end of the plasticizing cylinder 32 coupled to the support cylinder 33. It is formed to be open. The vent port 50 is formed through the upper portion of the front cylinder of the supply port 37. A pressure reduction suction unit 50a is connected to the vent port 50, and an inert gas pressure transfer unit 37a is provided at the supply port 37.

The tip of the screw 30 is attached with a check valve 38 having a tip-shaped cone and a mushroom-shaped object. A recess corresponding to the front end of the body is formed inside the front end of the plasticizing cylinder 32 in which the check valve 38 is disposed, thereby communicating with the discharge passage around the check valve 38. Flow passages are formed. In addition, a ring valve seat 39 (annular valve seat) is provided in the cylinder to which the inclined rear surface of the check valve 38 faces.

Although the flow path varies depending on the resin, when the diameter of the check valve 38 is 36 mm, a flow gap 31a of 1.0 to 1.5 mm is formed between the check valve 38 and the ring valve seat 39. In addition, it is designed to form a sufficient flow path between the check valve 38 and the wall of the groove. When the flow gap 31a is 0.5 mm or less, the heat generation in the plasticizing cylinder is large, and when the flow gap 31a is 2.0 mm or more, it takes a long time to close the valve, thereby preventing backflow of the metered resin. It is easy to do it.

The resin passage 13 is composed of a plurality of capillaries 40, a plurality of band heaters 41 are disposed in the outer peripheral portion and the mixing member 42 is disposed in the upper portion. The capillary tube 40 is inclinedly provided with joints 40a, 40b and joints across the inlet 25 of the injection cylinder 22 and the outlet 31 of the plasticizing cylinder 32. When the plasticized resin passes through the resin passage 13, the temperature of the plasticized resin becomes more uniform.

The injection apparatus 11 and the plasticizer 12 are connected to the upper and lower two stages integrally by fixing the support cylinder 33 on the support 28 installed in the injection apparatus 22, clamping ( mounting the hydraulic cylinder 24 of the injection device 11 on a base block 16 which is connected via a nozzle touch cylinder 15 of a fixed plate 14 of a clamping device (not shown) and is slidable; It is provided on the base 17 by being fixed. The tip of the nozzle 21 is in contact with the gate of the information recording disk die 51 attached to the base clamping device.

The mold 51 is composed of a stationary mold and a movable mold like a conventional mold, and a plurality of disk forming cavities 52 are formed on the divided surface between the stationary mold and the movable mold. The plurality of cavities 52 are in communication with the gate of the mold through the hot runner 53 disposed in the fixed mold, and one side of each cavity 52 is disposed in a state where the stamper is stretched out.

Next, an injection molding method of the information recording disc using the injection apparatus will be described.

By supplying hydraulic oil to the rear chamber (chamber) of the hydraulic cylinder 34 to move the piston (34a) and the rotary shaft 33a forward with the screw 30, the valve seat to open the valve ( Separate the inclined rear face from 39). At about the same time, the screw 30 is rotated together with the rotary shaft 33a by the rotary drive unit 35, and an inert gas such as nitrogen gas is pumped into the cylinder through the supply port 37. .

At this time, granular polycarbonate is supplied to the inside of the plasticizing cylinder 37 via the supply port 37 as a resin material. The resin material is melted and kneaded. That is, the cylinder is sequentially plasticized while the resin material is plasticized in an inert gas atmosphere supplied between the supply port 37 and the vent port 50 by heating by the band heater 36 and rotation of the screw 30. Is pushed forward.

By the melting and kneading, the moisture contained in the resin material becomes vapor, and the residual units are also released from the molten resin. This volatile gas is sucked out from the vent port 50 to the outside, and does not remain in the molten resin in front of the vent port 50. The molten and kneaded resin sequentially reaches the distal end of the cylinder and passes through the outlet 31 in communication with a flow gap 31a between the check valve 38 and the valve seat 39. To be discharged.

In the resin passage 13, the granularity and stirring of the resin is repeatedly performed, and the resin flows through the inlet 25 while kneading. Furthermore, since the resin flows through the inlet to the front end of the injection cylinder 22, the resin is accumulated and measured at the front end of the cylinder while pressing the front end surface of the plunger 20 to move the plunger backward. This metering is performed until the plunger 20 moves backward to the set position.

When the plunger 20 stops moving backward to the weighing stop position, the rotation of the screw 30 is stopped and plasticization of the resin is temporarily stopped. In addition, since the front area of the body of the check valve 38 is larger than the inclined rear area, there is a difference in area. Therefore, the resin pressure during plasticization is higher than the front of the body, and the plasticizing cylinder side is higher than the front of the body. Since the acting pressure is greater, when the hydraulic oil is applied to the front chamber of the hydraulic cylinder 34, the screw 30 is not affected by the resin pressure of the plasticizing cylinder and immediately the rear surface of the body It moves backward to the point where it contacts the valve seat 39. As a result, the valve is blocked in the tip of the plasticizing cylinder 32 to reliably block the flow of the resin.

Further, since the valve opened as described above is caused by the backward movement of the screw, extrusion of the resin on the front surface of the valve body does not occur, and the metering stop position of the plunger 20 is stabilized. As a result, a predetermined amount of resin is improved in the front portion of the plunger 22.

When the plunger is moved forward with the check valve 38 closed, the resin measured in the injection cylinder is injected into the mold 51 via the nozzle 21. The injection pressure applied by the plunger 20 also acts on the plasticizing cylinder side through the resin remaining in the resin passage 13. However, since the check valve 38 is in a closed state, the back flow of the resin to the plasticizing cylinder side is prevented, so that the entire amount of the metered resin passes from the nozzle 21 through the hot runner 53 to all the cavities. Filled with 52 to form a thin disk, and at the same time transfer of the pit from the stamper.

When the completion of the injection process is confirmed, the screw 30 moves forward by the hydraulic cylinder 24 to open the valve, and rotates by the rotary drive unit 35 to start metering new resin.

As described above, according to the molding method, plasticization and injection capacity of the resin are more stable than plasticization in the injection cylinder, so that the error of weighing repeatedly performed is minimized and injection filling of the same amount is possible every time. Become. Therefore, it is desirable to increase the number of cavities in the mold and to perform a plurality of moldings at the same time. This is also preferable in that the larger the amount of resin required in one molding, the more stable it is, and by performing a plurality of moldings at the same time, a more stable information recording disc can be produced. Therefore, the present invention has a feature capable of simultaneously performing a plurality of moldings.

Claims (5)

In the injection molding method of the information recording disk, Supplying the resin material to the supply port of the injection apparatus provided with the vent port without omitting preliminary drying of the resin material; Melting and kneading the resin material by the injection device and vaporizing a volatile component such as water in the hand by heating and discharging it from the vent port to the outside of the cylinder; Measuring the molten resin; Manufacturing a thin information recording disc by injection-injecting resin into a mold in which a molding cavity of the information recording disc is formed; The inside of the cylinder between the supply port and the vent port of the injection apparatus is an inert gas atmosphere, and the inert gas prevents oxidation of the resin material during melting and kneading of the resin material. Injection molding method of disc. The method of claim 1, The injection apparatus is an information recording disk injection molding method, characterized in that the in-line screw injection apparatus. The method of claim 1, The injection device is a screw pre-plasticization injection device in which a screw vent hole is formed, The resin material is melted and kneaded by the rotation of a screw in a plasticizing cylinder provided with a vent port, and at the same time, volatiles such as moisture of the resin material are discharged from the vent port, and plasticized. The plasticized resin is conveyed to the front part of the injection cylinder with the plunger and weighed, And injection molding the resin measured by the plunger into a cavity in a disk forming mold to produce a thin information recording disk. The method according to any one of claims 1 to 3, And the information recording disk is manufactured in plural at the same time by a mold having a plurality of cavities formed therein. The method according to any one of claims 1 to 3, And the resin material is polycarbonate.